Control of the location of feed wire during a metal deposition process is important to achieving high quality material deposition. In conventional gas metal arc welding (GMAW) processes, uncontrolled wire wandering can occur due to curvature of the wire from winding on a spool causing random lateral motion at the point of delivery. This curvature is quantified by two parameters: 1) cast—the diameter of a loop of wire laying on a flat surface; and 2) helix—the pitch or lift-off of a loop of wire laying on a flat surface. Minimum cast and maximum helix are normally controlled by weld wire manufacturers to American Welding Society specifications as they affect wire deflection and point of delivery during welding. U.S. Pat. No. 4,580,026 describes an in-line electrical resistance hot wire weld feed system that helps deliver a feed wire in a straight fashion by annealing the wire during delivery, which removes the curved cast and helix of the wire caused by spooling.
Laser beams are also used to melt filler metal onto a substrate for welding, cladding, and additive fabrication. Often, powdered feed material is used. However, laser deposition of wire feed material requires coordinating the wire feed position with the laser power delivery spot. It is challenging to mechanically compel the tip of a small diameter wire (such as 1 mm) to coincide with a similarly sized focal spot of a laser beam, especially when both are motion-controlled independently. For example, the laser beam may be controlled by galvanometer-driven optics, and the wire may be controlled by a mechanical manipulator and feed system.